Citric Acid is also known as an Alpha Hydroxy Acid. Alpha hydroxy acids are a group of natural aicds found in foods, citric acid (citrus fruits), glycolic acid (sugarcane), lactic acid (sour milk), malic acid (grapes). They help to exfoliate the top layers of dead skin cells. Alpha hydroxy acids also help to increase smoothness and reduce dark spots. Thus, the acids are typically found in skin care and anti-aging formulas. The pH and concentration of the acid contribute to how rapidly it is absorbed by the skin - the lower the pH, the more rapidly it is absorbed.